When free radicals attack biological cells and tissues they can be incredibly destructive. They damage our cells, which can mean premature aging, reduced immune function, inflammation and ultimately degenerative disease. Among our primary defenses are the antioxidant nutrients, of which the most well known are vitamins C and E. The biological activity of antioxidants is enormously important to our health. Antioxidants have been known to neutralize free radical damage, rendering them all but harmless. Aging and deterioration in human cells is caused by the chemical process of oxidation. Scientists theorize that when pollutants, chemicals, and toxins such as cigarette smoke or food additives combine with oxygen in your bloodstream, they produce unstable (and harmful) molecules called "free radicals". Free radicals cause cells to die off faster than your body can produce new ones. As you get older, your body produces fewer new cells to replace the ones that die. This combination results in the aging process. When free radicals attack human cells, they weaken cell walls and erode them to the core. These weakened cells age rapidly, inviting disease and infection because of their unhealthy state. Scientists have identified a group of vitamins called antioxidants which choke off the supply of oxygen to the free radicals, thereby rendering them almost harmless. With free radicals thus neutralized, human cells and tissue remain younger and healthier.
The term nutriceutical appears to have been introduced initially by Stephen de Felice, M.D., director of New York's Foundation for Innovation in Medicine. The term nutriceutical is intended to describe specific chemical compounds found in foods that may prevent disease. The term phytochemical is a more recent evolution of the term that emphasizes the plant source of most of these protective, disease-preventing compounds. A true nutritional role for phytochemicals is becoming more probable every day as research uncovers more of their remarkable benefits. In fact, the term phytonutrient better describes the compounds' status. Someday, phytochemicals may indeed be classified as essential nutrients. A significant body of research suggests a strong link between diet and health. Current studies are showing that as we move away from the diet of our ancestors we succumb to modern diseases. Evidence of this can be seen in societies such as the centenarian tribes that live in remote villages in the Andes mountains and who still embrace traditional dietary practices. These people have been reported to live extraordinarily long lives that are free of such illnesses as cancer, heart disease and arthritis. Since few people in our modern society live today as do the tribes in remote Andean villages, researchers have examined epidemiological evidence from modern societies for clues to the diet-disease connection. On the basis of such studies, biochemical researchers have identified certain phytochemicals that aid the body in maintaining health and combating disease. As an overall guideline, health authorities recommend that we consume diets rich in whole grains and fresh fruits and vegetables as well as reduce fat and animal-protein consumption.
The amino acid L-histidine having the chemical structure shown below ##STR1## is one of the 10 essential amino acids which cannot be synthesized by the human body and therefore must be obtained by the diet. In addtion to histidine's routine metabolic role as a protein building block, histidine is an effective scavenger of toxic oxygen species and therefore is useful in the protection of cells and tissues from a variety of inflammatory disease processes.
Several in vitro and in vivo laboratory studies have demonstrated histidine's antioxidant effects. The antioxidant effect observed with histidine has been attributed to its ability to scavenge highly reactive oxygen species, particularly singlet oxygen (.sup.1 O.sub.2) and hydroxyl radical (.circle-solid.OH) produced by the degradation of hydrogen peroxide and molecular oxygen. In one study [A. K. Vinnikova et al "Singlet Oxygen-induced inhibition of cardiac sarcolemmal Na.sup.+ K.sup.+ -ATPase", J. Mol. Cell. Card., 24: 465-470 (1992) and R. C. Kureja et al "Singlet oxygen interaction with Ca.sup.2+- ATPase of cardiac sarcoplasmic reticulum"; Circ. ReS. 69, 1003-1014 (1991)], histidine afforded dose-dependent protection to sarcolemmal Na.sup.+ -K.sup.+ -ATPase and Ca.sup.2+ ATPase subjected to singlet oxygen-mediated damage in vitro. The researchers of the above studies compared the effects of histidine, superoxide dismutase (SOD) and catalase in sarcoplasmic reticulum preparations and noted that histidine was efficient at protecting the enzymes' integrity due to its unique ability to scavenge singlet oxygen species. In another study [M. A. Khalid et al "Histidine protects bovine endothelial cells against anoxia reoxygenation injury by scavenging singlet oxygen"; Circulation, 86: 1223 (1992)] bovine endothelial cells treated with histidine were protected from post-anoxic reoxygenation injury.
Other studies [A. K. Vinnikova et al "Singlet Oxygen-induced inhibition of cardiac sarcolemmal Na.sup.+ K.sup.+ -ATPase", J. Mol. Cell. Card., 24: 465-470 (1992); Q. Cai et al "Antioxidative properties of histidine and its effect on myocardial injury during ischemia reperfusion in isolated rat heart", J. Cardiovasc. Pharmacol.; 25: 147-155 (1995); R. C. Kukreja et al "Protective effects of histidine during ischemia-reperfusion in isolated perfused rat hearts", Am. J. Physiol., 264:H1370-H1381 (1993) and R. C. Kukreja et al "The oxygen free radical system: from equation through membrane-protein interactions to cardivascular injury and protection", Cardiovasc. Res. 26: 641-655 (1992)] have shown that canine and rodent heart preparations subjected to ischemia/reperfusion injury were protected from singlet, hydroxyl radical and superoxide anion damage by the application of L-histidine.
Recent in vivo studies in rats subjected to coronary artery ligation and reperfusion demonstrated that 3 mM histidine could reduce ventricular infarcts and the duration and severity of arrhythmias, and was more effective than superoxide dismutase at achieving this protectant effect.
In applicants pending U.S. application Ser. No. 08/718,705 filed Sep. 27, 1996, it is disclosed that histidine has a strong protective effect against intestinal fluid accumulation induced by both Salmonella infection and by cholera toxin in a mouse model. S. typhimurium-induced intestinal fluid accumulation was reduced 47% in histidine-treated mice, and evaluation of tissues by light and electron microsocopy showed significant protection of the intestinal mucosa by histidine. In addition, mean cholera toxin-induced intestinal fluid accumulation was reduced 54% in histidine-treated mice. The fact that these two diarrhea-inducing agents act by different mechanisms indicates that histidine's intestinal protective effects may be very broad.
In a study dealing with mechanism of action [M. C. Erikson et al, "Influence of histidine on lipid peroxidation in sarcoplasmic reticulum"; Arch. Biochem. Biophys. 292: 427-432 (1992)], the effects of histidine on lipid peroxidation in an in vitro system derived from fish muscle sarcoplasmic reticulum were shown to be dependent on the order of addition of components (histidine, ferric iron, and reduced nicotinamide-adenine-dinucleotide). The studies by Erikson et al suggest that histidine's protective effect in vivo may be related to its ability to interfere with the reduction of ferric iron. Ginsburg [I. Ginsburg, "Cationic polyelectrolytes: Potent opsonic agents which activate the respiratory burst in leukocytes"; Free Radic. Res. Commun. 8:11-26 (1989)] has shown that polyhistidine or histidine complexed to the free radical scavengers, SOD or catalase, enhanced their ability to function as intracellular antioxidants. In vitro and in vivo studies [A. A. Boldyrev, "Natural histidine-containing dipeptide carnosine as a potent hydrophilic antioxidant with membrane stabilizing function"; Mol. Chem. Neuropathol., 19: 185-192 (1993) and O. V. Naumova et al; "Effect of carnosine on liver enzyme systems of animals subjected to radiation"; Biokhimiya, 57: 1373-1377 (1992] with the dipeptide carnosine (.beta.-Alanine-L-histidine) indicated that its radioprotective and membrane stabilizing effects were attributed to the actions of histidine, not alanine. Carnosine functions as a pH buffer and as a chelator of a variety of metals, which contributes to its oxygen scavenging profile.
The prior art is silent regarding nutriceuticals and/or dietary supplements containing histidine as a cytoprotective agent and as an antioxidant/free radical scavenging agent. Furthermore, the prior art is silent on nutriceuticals and/or dietary supplements incorporating histidine as a scavenger of singlet oxygen. The present invention provides nutriceutical formulations incorporating histidine as an antioxidant/free radical scavenger and therefore fills a long-felt need not currently available in the market place.